1. Field of the Invention
The present invention relates to a weather strip comprising a sectionally U-shaped flange gripping portion having an insert buried therein and gripping lip portions formed inside, and seal portions integrated with the flange gripping portion.
The present application is based on Japanese Patent Application No. Hei. 11-70712, which is incorporated herein by reference.
2. Description of the Related Art
The door opening-trimming weather strip shown in FIG. 1 or the trunk weather strip shown in FIG. 2 comprises a sectionally U-shaped flange gripping portion 14 having an insert 12 buried therein, a hollow seal portion 16 of sponge rubber, and a lip seal portion 18 of sponge rubber.
Generally, the flange gripping portion 14 including gripping lip portions 20 and 21 is formed of vulcanizate (solid rubber) of a nonfoam-recipe EPDM rubber composition by extrusion molding, or the like. On the other hand, the hollow seal portion 16 and the lip seal portion 18 are formed of vulcanizate (sponge rubber) of a foam-recipe EPDM rubber composition by extrusion molding so that the seal portions 16 and 18 are integrated with the flange gripping portion 14.
EPDM is excellent in weather resistance, ozone resistance, and so on. EPDM is also good in low-temperature characteristic. EPDM is easy to satisfy the required characteristic of weather strips. Accordingly, EPDM is used as a material for the weather strips.
Further, in the case of a weather strip configured as described above, the weather strip is bent two-dimensionally or three-dimensionally at least in corner regions when the weather strip is assembled to a flange portion 22 which is, for example, annularly formed in a circumferential edge of a door opening portion. The flange portion 22 not only has a double-ply region constituted by a combination of an outer panel 24 and an inner panel 25 as shown in FIGS. 1 and 2 but also generally has a single-ply region constituted by one panel or a triple-ply or quadruple-ply region constituted by a combination of two panels and one or two reinforcement panels interposed between the two panels.
Therefore, the shapes of the gripping lip portions 20 and 21 were set so that the largest insertion load required when the flange gripping portion of the weather strip was inserted onto the flange portion was set in accordance with the thickest region of the flange portion and the smallest extraction load required when the flange gripping portion was extracted from the flange portion was set in accordance with the thinnest region of the flange portion.
Further, in the case of the aforementioned weather strip, it is necessary to secure the smallest extraction load. This is for the reasons as follows. If the smallest extraction load is not secured, for example, the bent region tends to be restored to its original condition after the flange portion is fitted into the weather strip. As a result, the flange gripping portion is displaced in an extracting direction, so that the seal position is shifted from its normal position. There is a possibility of occurrence of a problem in sealing property.
If the smallest extraction load (the load required when the flange gripping portion is extracted from the thinnest region of the flange portion) is to be secured, the largest insertion load (the load required when the flange gripping portion is inserted into the thickest region of the flange portion) increases reversely. As a result, workability in fitting the weather strip to the flange portion is reduced.
Incidentally, it is thought of that the gripping force of the gripping lip portions is formed while the angle of inclination is changed in accordance with the plate thickness of the single-ply, double-ply or triple-ply region, or the like (Japanese Patent Publication No. Hei. 6-340238, Japanese Patent Publication No. Hei. 10-6379, and so on). The production by this method is, however, of no practical use because controlling is difficult.
It is further thought of that the gripping lip portions of the flange gripping portion are formed of sponge rubber for the purpose of reducing the largest insertion load (see Japanese Patent Publication No. Sho. 52-77324, etc.). When the gripping lip portions are formed of sponge rubber, the gripping force of the flange gripping portion is, however, insufficient so that it is impossible to secure the smallest extraction load.
Taking the above description into consideration, an object of the present invention is to provide a weather strip in which the smallest extraction load on a flange gripping portion can be secured while the largest insertion load is set in a standard range.
Although description will be made here about a door opening-trimming weather strip or a trunk weather strip provided in the automobile body by way of example, the description can be applied also to other weather strips such as a quarter window weather strip, a door weather strip, etc.
The inventors have found that the aforementioned problem can be solved when the flange gripping portion of the weather strip is formed of microfoam rubber with specific gravity in a predetermined range. As a result, the inventors have hit on the weather strip having the following configuration so as to solve the aforementioned problem.
That is, there is provided a weather strip of a rubber material which comprises a sectionally U-shaped flange gripping portion having an insert buried therein and gripping lip portions formed inside, and seal portions integrated with the flange gripping portion, wherein at least the gripping lip portions in the flange gripping portion are formed of microfoam rubber in which specific gravity of vulcanizate is in a range of from 0.9 to 1.0.
Preferably, if the microfoam rubber is provided to have the specific gravity of vulcanizate in a range of from 0.95 to 1.0, the aforementioned problem can be solved more easily.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.